When I was about 2 years old I saw my older brother naked briefly when my mom was putting him in the bath. I was convinced a penis wasn't attached to the body, but rather something boys had to hold between their legs. If they moved their legs apart, it would fall off. No idea how I came to this conclusion.
A childhood belief about rude bits

others believed things like this
- i used to believe that when you did the splits your legs would fall off.Anon
- when i was little i always asked my mom if my aunt had ant legs or people legs.— kelly
- If you undo your belly-button with a screwdriver, your legs will fall off.— Toby
- My Dad convinced me that Manx cats had no tail - and only three legs.— Jim
- I used to think a female daddy-long-legs was called a "mummy-long-legs".Anon
- I believed that wind was caused because the trees moved. I was completely sure my conclusion was correct.— Glenr